[The spinning top] drops at the end, that's when I come back on. Young people say to me, "At the end, when you're there, is it a dream or is it real." If I'm there it's real, because I'm never in the dream. I'm the guy who invented the dream.

Caine's simplistic explanation has already received naysayers. IndieWire was quick to poke holes in Caine's theory, theorizing that Caine indeed could be part of the dreamworld.

Really wanting to challenge Caine’s argument, I went back and watched more. And this time also caught the line Caine says in his first scene when he solemnly says, "come back to reality, Dom. Please." In the context of the conversation it seems as if he’s just saying the equivalent of "let’s be serious." Within the whole narrative, though, the phrasing comes off as something more akin to a literal plea to "wake up."

Neither theory is that strongly supported, leaving the ending as interpretive as before. Perhaps Nolan will clear everything up on the DVD, but considering how closely guarded the movie was about its secrets before the movie opened, we're guessing Nolan might keep the ending to himself.